In pathology and other cell analysis, it is generally desirable to isolate substantially only the specific cell sample from the biological sample, for example, to perform a DNA analysis and the like. Such selective isolation of desired cell sample allows a more accurate analysis without a significant contamination from other none desirable cells.
Conventional methods are expensive, labor intensive and/or unable to provide the desired cell sample in a suitable concentration for analysis. In addition, some conventional cell extraction methods are slow and/or unsanitary. One example of conventional cell extraction method involves using a mouth pipette to aspirate the desired cell sample from a glycerol covered slide and blowing the sample into an appropriate test tube. The glycerol acts as an inert medium that helps transport the cell sample into the pipette. This method creates the risk of contaminating the patient sample with operator cells and of inadvertently aspirating potentially hazardous patient cellular material into the mouth of the operator.
Another conventional method for extracting the cell sample uses a scalpel and ethanol. This method is generally more tedious and required much greater skill and practice in order to perfect. Because of the small size of the cells, the movements of the scalpel require great precision. Such precision requirement makes this method an art form that is difficult to master and creates the need for a method to cleanly remove cells that have been dislodged from the microdissected slide.
Majority of conventional methods for obtaining a desirable cell sample for analysis from a tissue include fixing the tissue section or sample on a sample immobilizing base having a film attached thereto (e.g. a coated slide glass) and cutting a desired area of the film by tracing a contour of the desired area on the tissue sample. Some conventional methods use a laser light to detach the desired area from the underlying immobilizing matrix and then transfer detached target cells to a second adherent surface from which they are washed for molecular analysis. This method is also technically challenging. When detaching the desired area using a laser light by tracing a contour of the desired cell sample area of a tissue section, the tissue section tends to deform during dissection due at least in part from a pressure generated by evaporation of the sample itself or a stress at an uncut part. Therefore, it is difficult to correctly cut the desired area even with a sophisticated and precise device like a laser, if the tissue section is particularly a deformable biological sample. Moreover, the DNA yield for the amount of time spent and the complicated equipment required is low. In addition, training requirements to master the laser capture device are considerable and the instrument must be adequately maintained by specialized personnel. Furthermore, laser equipment is often expensive and requires a relatively high maintenance.
For small samples that are increasingly being used to guide targeted treatments it is especially important to maximize efficiency of tumor cell collection, smaller amounts of DNA tend to amplify artifactual DNA base alterations that are an inevitable accompaniment of tissue processing methods conventionally used in clinical practice. Multiple sections may need to be dissected in order to maximize DNA yield which may be difficult to achieve with conventional methods and laser capture methods.
Accordingly, there is a need for an apparatus that is more cost effective and easier to use for collecting a desired cell sample from a tissue sample. In addition, there is a need for a simple apparatus and method that can maximize the number of tumor cells that can be harvested from a given tissue section.